Legislative Competence Orders (LCOs) are a type of secondary legislation which transfer the power to make laws on specific policy areas from the UK Parliament to the Welsh Assembly.
They are so-called because the scope of the National Assembly for Wales's power to create "measures", or Welsh laws, is known as its legislative competence.
The "fields", or broad policy areas, over which the Welsh Assembly has legislative competence are listed in Schedule 5 of the Government of Wales Act 2006.
With each field are listed "matters" - specific policy areas that the UK Parliament has granted the Welsh Assembly the right to legislate on.
To make measures, the Assembly currently asks the UK Parliament to approve new LCOs.
Legislative competence may also be extended by an Act of Parliament.
The LCO system will no longer be used after the assembly elections on 5 May 2011.
A majority of voters in a referendum on 3 March 2011 voted to give the Welsh Assembly the ability to pass laws on all subjects in the 20 devolved areas without first needing the agreement of the UK Parliament.
Proposed laws will be called "bills", and enacted laws will be called "acts".